Everyone turns up for a car chase at the end of the world, and the cars won't start.

Alfonso Cuarón's Children of Men is a movie of exquisite direction, and I'm madly in love with the action scenes. Violence in Cuarón's movie is sudden and unemphasized: the camera doesn't flinch, the sound mixing doesn't dwell, and that gives the action a terrible power. Children of Men knows a subtle secret.

Clive Owen's in a paramilitary compound with the last pregnant woman on Earth. He needs to sneak her away. In the early morning he creeps out, sabotages the other cars, bundles his friends into the last working automobile, and gets it rolling. But the car won't start! Alarms start ringing. Gunmen converge.

So Clive and buddies have to get out and start pushing.

And it's thrilling. It had me keyed up in a way car chases never do — even though it's just an alcoholic pushing a car down a hill, chased by a barking dog and a bearded goon who looks like Techno Viking. Compare to the endless car chase in The Matrix Reloaded, where hackers fight ghosts and evil agents on top of freeway traffic and Morpheus explodes a car with his katana inside a simulation operated by the post-apocalyptic machine overlords.

Why does the danger in Children of Men feel so much more immediate?

One reason is that we understand the rules. We don't know how to kill a ghost, or how many sprays of bullets it'd take to hit Trinity. (Every time an action movie shows a blazing gun that hurts nobody, it spends a little bit of its ability to make us scared of guns.) But we know that if the Viking thug catches up to the car, he'll grab Clive Owen and kill him. We know that if the car doesn't start before the bottom of the hill, they'll be stuck in the mud.

An action scene grips us when we know what the action could cost. Superman gets punched through a building? Clearly that's bad, but it doesn't feel like much. But watch a torturer slide a knife under a man's thumbnail, and we cringe.

And we understand the consequences of failure. We feel them right in our gut. Children of Men's already taught us, by gunshot and bomb, by long unwavering camera takes and naturalistic acting, that violence in this movie is abrupt, awful, and intimate. One bullet is all it takes. This is the subtle secret: violence and grief can hit us from nowhere, in a place we thought was safe, and we are so, so afraid of that. Fiction can use that fear.

Even Children of Men's plot puts weight and tension on every single human life. The movie's themes conspire with the camera to support the action. By teaching us that its characters are fragile, breakable people, Children of Men makes a morning hill more dangerous than a freeway.